Ignition system



May 27, 1969 M. E. HANTACK I 3 6 IGNITION SYSTEM Filed June 27, 1966 I IN VEN TOR. mam/z n/f/fla United States Patent Int. Cl. F23n 5/00 US. Cl.431-70 Claims ABSTRACT OF THE DISCLOSURE An electrical system for theignition of fuel wherein a spark discharge ignition device isdeenergized upon ignition of fuel and wherein there is also 'a decreasein consumption of power from the electrical source upon such ignition.

This invention relates to electrical systems for the ignition of fuelburning devices and the like, and particularly to a gaseous fuel burner.

More specifically, the invention concerns an arrangement of theabove-mentioned type which acts as a safety device for preventingdangerous situations that may develop in the event a component of theelectrical installation should fail, including interruption of the powersupply or the source of current, fuel flow stoppage, failure to ignite,and flame extinguishment.

These desirable features are provided by the present novel circuitrythat also includes an automatic ignition system of the high-voltagespark discharge type that is deenergized upon ignition of fuel so as toincrease the operating life of the ignition system, and also providesfor a decrease in the consumption of power from the electrical source.This novel circuit eliminates many moving parts, and eliminates radioand television interference and noise.

The present novel ignition system employs a pair of' SCR(silicon-controlled rectifiers), each being arranged parallel withrespect to each other, in two more or less different circuits, with oneSCR being arranged in series with the ignition transformer and the flameresponsive switch, and the second being arranged in series with thesolenoid of a fuel valve. The silicon-controlled rectifiers, inconjunction with a pair of diodes, change alternating current intocontrolled pulsating direct current that permits it to work efficientlyat different current flow depend ent upon the E.M.F. imposed upon theemitter. In particular, by arranging the emitter of the SCR associatedwith the solenoid whereby its current source is controlled in responseto burner flame, the current flow through the solenoid may be adjustedto provide a high flux density for the solenoid valve actuation uponstart-up, and low flux density for normal run condition so that thecurrent flow through the solenoid is consequently maintained at theminimum amount required to supply a flux density that will hold thevalve in open condition. The entire circuitry employs additional safetydevices associated with the two parallel legs thereof to accordinglyprovide safety features generally considered either desirable ornecessary for a system such as described herein.

One object of this invention is to provide for an electric igniting andfuel supply control arrangement for heating systems that require a lowcurrent drain after start-up.

Another object of this invention is to provide an electric igniting andfuel supply control arrangement that eliminates many moving parts, andreduces radio and television interference and noise to a minimum.

It is another object of this invention to provide for an arrangement ofthe type set forth which operates in a maner that the fuel valve isopened simultaneously with 3,446,565 Patented May 27, 1969 theactivation of the ignition device, so that fuel to the burner isimmediately ignited upon flow through the fuel valve.

Still another object of this invention is to provide an ignition andfuel control device which cuts off upon fuel flow stoppage, or flamefailure, after one re-ignition attempt.

Other objects of this invention will become apparent to those skilled inthe art from the following drawing and specification, which shows oneillustrative embodiment of the invention that is also defined andembraced by the annexed claims.

Seen in the present drawing is a schematical representation of the novelignition control system, wherein conventional circuit components areconventionally illustrated, but arranged in a novel electricalconfiguration. The system includes a solenoid 10 adapted to actuate afuel valve 11 that is usually fiow connected to a burner as suggested bythe numeral 12. The device includes a flame responsive switch 14 placedin heat-responsive or heat-sensing relationship to the burner, so thatthe normally closed switch will assume the open position when heated. Asource of current, illustrated by numeral 16, provides electricalconductor lead lines L1 and L2 with a suitable supply of current.

Looking now to the details of the figure, there is seen schematicallyillustrated therein a thermostat 18 which, in this particular instance,is shown as having a bi-metal strip that may be warped in accordancewith the ambient temperature, so as to close contacts 20 and 21 uponheat demand and open contacts 20 and 21 when the desired temperature hasbeen obtained. The fixed contact 21 connects to the junction 22 toprovide a source of current along the two indicated electrical paths toform two circuits, the first of which flows through the diode 23,resistance 24, and terminal 25 where the current again splits to providea source along two different paths, one of which supplies the SCR 26with a current source through the solenoid 10. The SCR 26 is furtherconnected so as to complete its circuit along the electrical pathidentified by terminals 27, 28, 29, and 30, warp safety switch bi-metalportion 32, movable contact 34, fixed contact 36, and terminal portion38 so as to complete the circuit at Ll. Hence, it is now clear that whenthermostat 18 demands heat by moving to the closed position (oppositethat shown in the figure), current flow is available to the SCR 26,assuming contacts 34 and 36 of the warp safety switch are closed. Withthe emitter, or triggering portion, of SCR 26 de-energized, insufiicientcurrent will flow along the before-described path to actuate the valve11 that is controlled by the solenoid 10.

A second circuit, including portions of the above described circuit,provides power to the igniter 60 along the path defined by L2,thermostat 18, terminal 22, flame responsive switch 14, terminal 41,diode 53, resistor 54, terminal 70, terminal 55, ignition transformer60, SCR 66, terminal 68, terminal 30, warp safety switch 32, andterminal 38 which completes the circuit back to the source at L1. Thelast-described circuit provides for current flow through the particularcircuitry involved when the system is in stand-by condition and theburner accordingly is not burnin but thermostat 18 is calling for heat.This last circuit will also cause the triggering circuits of SCR 26 and66 to become energized by the following paths of current flow:

With the thermostat 18 and flame responsive switch 14 closed, current isavailable at terminal 41 where it branches into two different paths,each of which trigger the particular SCR to which it is electricallyconnected. The SCR 26 that actuates the solenoid 10 is triggered by afirst triggering circuit wherein the current flows from terminal 41,

resistor 42, diode 43, and resistor 44 whereupon a triggering currentsupply is then imposed upon the SCR 26 to allow current to then flowalong the first abovedescribed path so as to energize the solenoid 10.The second path of current flow that forms the second triggering circuitfrom terminal 41 to the SCR 66 is along the path defined by diode 53,resistor 54, terminal 70, resistor 72, terminal 73, neon firing light orbulb 74, and to the emitter of SCR 66 which is triggered, therebyallowing a large flow or surge of current to pass through or along thesecond flow path that includes the ignition transformer 60.

The design of the neon firing light 74- is conventional and fires, orbecomes highly conductive, only when the voltage applied across its twoterminals exceeds a predetermined critical value. The combination of theresistor 72 and the capacitor seen at 75 determine the rapidity orfrequency with which the neon firing light produces an upon the emitterof the SCR 616. Each pulsation of current that flows across the firinglight produces a large flow of current through the ignition transformer60, and accordingly each surge of current produces a spark at electrodes62, which are located adjacent the burner 12 that is desired to beignited. The resistance 82 and capacitor 83 modify the action of thefiring light 74 upon SCR 66 so as to produce a hot spark at the sparkgap or electrodes 62.

As will be readily recognized by those skilled in the art, rectifiedline current from rectifier or diode 53 flows through resistors 54 and72 to charge capacitor 75 at a rate determined by the time constant ofthe resistance and capacitance of elements 54, 72, and 75. The E.M.F.across capacitor 75 is applied fully across the neon lamp 74 so thatwhen the capacitor reaches a certain critical value, the gas in the neonlamp will break down and effectively short-circuit the emitter toterminal 73. As a result, strong conduction of SCR 66 will occur throughthe second described circuit comprised of diode 53, igniter 60,terminals 68 and 30, and to the source through warp safety switch 32.During this process the capacitor 75 is substantially completelydischarged, and neon lamp 74 becomes extinguished so that the cycle mayagain commence with the recharging of capacitor 75. Hence, in thismanner, ignition sparks are produced at electrodes 62 at a regularlyrepeated rate determined by the above time constant.

The heater 46 is in heat transfer relationship with the bi-metal portionof warp switch 32 and is connected to the source throughflame-responsive switch 14 and thermostat 18, which provides a seriesflow path of current along these series connected elements from thesource of current 16 as previously detailed.

In operation, and with the ignition system in the illustrated stand-bycondition of the figure, the thermostat 18 will be in its normally cold,and hence opened, position so that no current flow occurs acrosscontacts 20 and 21, and accordingly the entire system is shut down andpower consumption is zero. At this time the normally closed solenoidactuated valve 11 will be closed and no fuel will be flowingtherethrough since solenoid is de-energized. The flame-responsive switch14 will be in its normally closed or cold position whereby contacts 39and 40 are closed as illustrated in the drawing since no flame ispresent at burner 12 at this time. The warp safety switch 32 will be inthe closed position since heater 4 6 is cold or de-energized, andcontacts 34 and 36 accordingly are in the illustrated normally closedposition. When the environment that is being temperature controlledcalls for heat, the thermostat 18 will move to the closed position,whereupon current will flow through solenoid 10 and SCR 26 along thebefore-described first flow path, while at the same time current flowfrom terminal 22 through flameresponsive switch 14 will provide theignition transformer 60 and SCR 66 with a current source. The neonfiring light 74 is likewise energized, and begins to trigger the emitterof the SCR 66. Current simultaneously flows from terminal 41 to theemitter of SCR 26, along the abovedescribed first triggering flow path.Since terminal por tion 41 is connected to the source of L2, the heater46 of the safety warp switch 32 begins to heat upand in a very shortpredetermined interval of time, will cause the bi-metal at 32 to warpthe contacts 34 and 36 to the open position, unless some interveningaction prohibits this occurrence. Upon SCR 26 being triggered, asuflicient amount of current flows through solenoid 10 to open valve 11,thereby supplying burner 12 with fuel. At this same time SCR 66 istriggered, and firing light 74 causes a saw-toothed wave of current topass through transformer with sufficient intensity to produce a hotspark at electrode 62, thereby igniting fuel flowing from the burner 12.Upon ignition of fuel at burner 12, the flame responsive switch 14 willbegin heating and will soon warp to the open position, therebydiscontinuing the flow of current through the movable and fixed contacts39 and 40 respectively, The flame-responsive switch 14 must open beforethe safety warp switch 32, in order to prevent shut-down of the system,and this is precisely what will happen under normal conditions ofoperation, for the reason that the flame-responsive switch 14 isdesigned with this in mind, whereby it will open prior to the safetywarp switch 32 opening. Upon flame-responsive switch 14 opening, thecurrent flow to terminal 41 is discontinued, and accordingly the heater46 begins to cool, the ignition transformer 60 is de-activated, and theemitter of SCR 26 is de-energized. Hence, it should now be evident thatwhen the flame-responsive switch 14 moves to the open position, the onlypath of current flow is from L2, then along the path described bysolenoid 10, SCR 26, terminal 28, warp safety switch 32, and back to thesource at Ll. In spite of the emitter of SCR 26 being de-energized,there is still a suflicient amount of rectified current flowing throughthe solenoid 10 to maintain the solenoid in a sufficient state ofmagnetism to maintain the valve 11 in the open condition, once it hasbeen opened; although there is insufficient current now flowing to haveoriginally moved the valve from the closed to the open position.Accordingly, there is a negligible current drain from the electricalsource as compared to the current requirements for start-up condition.The system will remain in the run condition under normal circumstancesuntil the environment in which thermostat 18 is placed has been suitablywarmed up, whereupon the thermostat will again open and return thecircuitry to its original stand-by condition.

Should the flame blow out (and this certainly should rarely happen in awell-designed system), the flame-responsive switch 14 will be cooled andmove to the closed position thereby again energizing SCR 26, igniter 60,and warp switch heater 46. The burner 12 normally will reignite and theflame will again heat the flame-responsive switch 14 to where it willswing to the open position and interrupt the current flow to the emitter26, the current flow to the ignition system, and the current flow to theheater 46.

In the unlikely event the burner should fail to re-ignite, the flameresponsive switch 14 will accordingly remain in the closed position,whereupon the heater 46 will remain energized, thereby causing thecontacts 34 and 36 to open and the entire system to be de-energized andshut down, save the following portion thereof, which includes closedthermostat 18, flame-responsive switch 14, heater 46, and terminalportion 38 connecting these components back to the source of current.Since the remaining portion of the circuit is deenergized, the valve 11will now return to the closed position, and accordingly shut off theflow of fuel to the burner 12. Since the thermostat is already callingfor heat, and heat cannot possibly be provided by the burner, it ishighly unlikely that the thermostat can ever again open until theengineer or attendant recognizes and cures the cause of the flamefailure, or the failure to reignite. In the case of fuel flow stoppage,the action of the ignition safety system will be identical to thebefore-described condition of flame blow-out.

Upon correction of the cause of the flame failure, the circuit may bereturned to stand-by condition by interrupting current flow through theheater 46, flame responsive switch 14, and thermostat 18. This actionwill permit the warp switch heater to cool, thereby allowing thecontacts of the warp switch to again close, whereupon the system is thenin the illustrated stand-by condition, with the thermostat 18 callingfor heat.

In the particular circuit shown in the drawing, the following values ofthe various circuit components have been found to provide suitableresponse rates and ignition spark frequencies:

24 ohms 200 26, 66 MCR 2604-5 42 ohms 1,000 44 do 12,000 54 do 1,000 72megohms 5.1 75 mfd. 200 v. D.C 0.947 80, 82 megohms 22 81, 83 mfd. 250v. D.C 20

It will occur to others skilled in the art that various minor changescan be made in the embodiment herein chosen by the inventor toillustrate his novel ignition system. Hence, while this invention hasbeen described in conjunction with the before-mentioned specific orparticular embodiment thereof, it should be understood that it may beembodied in many different forms from the abovedescribed withoutdeparting from the scope of the invention as defined by the appendedclaims.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. In a fuel burning control system including solenoid operated valvecontrol means for supplying fuel to a burner, and a source of electricalpower, the improvement comprising: ignition means associated with aburner and responsive to ignite fuel emanating from the burner when theignition means is energized; first circuit means for supplying a largecurrent to said valve control means when said igniter is energized andfor supplying a small current to said valve control means uponde-energization of said igniter, said first circuit means including anSCR series connected with the solenoid of said valve control means;second circuit means for supplying a current to said igniter; a firsttriggering circuit for actuating said first circuit means; a secondtriggering circuit for actuating said second circuit means; said firstand second triggering circuits having conduit means connected to thesource of power and including means responsive to the burning of fuel tointerrupt the power thereto; whereby said igniter is energized uponenergization of said valve control means, and de-energized upon the fuelbeing ignited.

2. The system of claim 1, wherein said second circuit means includes anSCR series connected with an ignition transformer, with said ignitiontransformer forming a portion of said igniter means; said first andsecond triggering circuits being connected by circuit means to theemitter of said first and second SCR respectively and to a commonterminal; and a flame responsive switch connected between said commonterminal and the source of electrical power.

3. The system of claim 2, and further including a warp safety switchseries connected between the source of power and said first and secondcircuit means; a warp safety switch heater connected between said commonterminal and said source of power; whereby failure of said flameresponsive switch to be actuated will permit said heater to open saidwarp safety switch to thereby discontinue the flow of power to saidfirst and second circuit means.

4. The system of claim 2, and further including a neon firing lampincluding circuit means associated with said second triggering circuitand connected to the emitter of said second SCR, and including a sourceof power, a capacitive means, and a resistive element associatedtherewith to control the firing rate of said neon lamp; said ignitionmeans including a spark gap associated with said transformer; wherebysaid second SCR is triggered by said second triggering circuit inresponse to the firing rate of said neon lamp to thereby apply asuitable voltage to said transformer to produce sparks across theelectrodes of the spark gap in order to ignite fuel from a burner.

5. The system of claim 1, wherein said igniter means includes atransformer having a primary and a secondary With a spark gapelectrically connected to said secondary to perform the ignitingfunction of claim 1; said first and second circuit means each includinga SCR and each being connected in parallel between two common terminalsand including a thermostat between one said terminal and the source ofpower and a warp safety switch between the remaining said terminal andthe source of power; a flame responsive switch in heat-responsiverelationship to the burner to be ignited and located in series with saidthermostat and said second circuit means; said first triggering meansbeing in series with said flame responsive switch and connected to theemitter of said first SCR; said second triggering means being connectedto the emitter of said second SCR and including a neon firing lamphaving capacitive-resistive means associated therewith to cause the lampto fire at a predetermined rate; and a heater associated with said warpsafety switch and including circuit means connecting said heater betweensaid source of power and in series with said flame safety switch.

6. The system of claim -5, and further including a parallel connectedcapacitor and resistor connected in parallel with said series connectedSCR and solenoid of said first circuit means; and a parallel connectedcapacitor and resistor connected in parallel to said series connectedSCR and ignition transformer of said second circuit means.

7. A control device for igniting and supervising the combustion processof heating systems comprising: a first circuit adapted to be connectedto a source of power and including electrical connecting means andseries connected thermostat, diode, resistor, fuel valve solenoid, SCR,and a warp safety switch completing the circuit to the source of power;a second circuit connected in series with said thermostat and includingseries connected flame switch, diode, ignition means, SCR, and with saidwarp safety switch completing the circuit to the source of. power; acommon junction in series with said flame-responsive switch having aheater, first triggering circuit, and a second triggering circuitconnected thereto; said heater having circuit means connecting to saidsource of like polarity with respect to said warp safety switch and inheat transfer relationship thereto; said first triggering circuit havingcircuit means connected to the emitter of said first SCR and including aresistance and a diode; said second triggering circuit having circuitmeans connected to the emitter of said second SCR and including thediode of the second circuit means and a current interrupting meansadapted to cause current to intermittently flow through the last recitedSCR to thereby produce a suitable igniting voltage for said ignitionmeans; whereby closing of said thermostat causes energization of saidsolenoid so as to move a fuel valve to the fuel flow position, and saidheater to be energized, and said ignition means to be energized; and,said flame responsive switch to move to the open position upon beingheated to thereby discontinue current flow through the heater andignition means, and to reduce the current flow through the solenoid.

8. The device of claim 7 wherein said ignition means includes atransformer having a primary and a secondary with said primary connectedin series with said second SCR, and further including a spark gapoperatively associated with said secondary thereof; said currentinterrupting means including a gaseous discharge device having a pair ofelectrodes that are highly conductive at a critical value of currentapplied therebetween and low conductive at values less than the criticalvalue; and timing means associated with said discharge device to causesuccessive pulses of current above the critical value to be 7 8 imposedon the plates of said neon tube; whereby said 10. The fluid fuel burnercontrol system of claim 9 transformer receives successive pulses ofcurrent in achaving: cordance with the pulse frequency of said gaseousdis- (c) an igniter circuit including: a silicon controlled chargedevice to thereby cause successive sparks to occur rectifier, anelectromagnetic device having a coil connected in series circuitrelationship with said silicon controlled rectifier; and means (b) alsosupplies trigat said spark gap.

9. A fluid 'fuel burner control system having:

(a) a fuel control valve circuit including: a silicon congering currentto the rectifier of (c).

trolled rectifier and an electromagnetic device having a coil connectedin series circuit relationship with References Cited said siliconcontrolled rectifier, a capacitor connected 10 UNITED STATES PA NTSinhurat'shiih F gg g g f i f ggf j g Islam 3,144,898 8/1964 Queever158l25 3,318,358 5/1967 Potts 158125 X (b) means supplying said siliconcontrolled rectifier with triggering current while the temperaturecircumambient said burner is below a predetermined 15 JAMES WESTHAVERPrimal), Examine" value. E. G. FAVORS, Assistant Examiner.

